The ALD810027 by Advanced Linear Devices is a member of the ALD8100xx family of Supercapacitor Auto Balancing (SAB™) MOSFETs. It is built with EPAD® technology and excels in voltage and leakage-current balancing for series-connected supercapacitors. By implementing one or more devices across each supercapacitor stack, these MOSFETs ensure precise voltage and current limits, guarding against over-voltages.

The chip offers unique, precise operating voltage and current characteristics for each of four SAB MOSFET devices. The key feature is its precision gate threshold voltage in the Vt mode, which is set at 2.70V. When the gate-drain source terminals (VGS = VDS) are connected together at a drain-source current of IDS(ON) = 1µA, the gate threshold voltage remains at 2.70V. Differential input voltages (VIN = VGS = VDS) generate an Output Current IOUT = IDS(ON), effectively configuring the device as a variable resistor that exponentially adjusts with VIN. This capability ensures that each supercapacitor in a series is balanced within its specified voltage and current limits.

For instance, applying VIN = 2.70V results in an IOUT of 1µA, and incrementing VIN by 100mV to 2.80V increases IOUT by about tenfold. Raising VIN to 2.94V leads to a hundredfold increase in IOUT, reaching 100µA. Conversely, a 100mV reduction in VIN to 2.60V reduces IOUT to one-tenth of its previous value to 0.1µA. Further decreasing VIN by another 100mV brings IOUT down to 0.01µA. Consequently, it exhibits near-zero power dissipation when connected across a supercapacitor charging to less than 2.50V.

The ALD810027's voltage-dependent characteristic on-resistance effectively controls excessive voltage rise across a supercapacitor. In series-connected supercapacitor stacks, as one supercapacitor voltage rises, the voltage of the others drops. Those that have the highest leakage currents will have the lowest supercapacitor voltages. The SAB MOSFETs connected across these supercapacitors exhibit complementary opposing current levels, resulting in minimal additional leakage currents beyond those caused by the supercapacitors themselves.

FEATURES & BENEFITS:

• Simple and economical to use
• Precision factory trimmed
• Automatically regulates and balances leakage currents
• Scalable for larger supercap stacks and arrays
• Achieves near-zero additional leakage currents
• Zero leakage at 0.3V below rated voltages
• Balances series and/or parallel-connected supercaps
• Active current ranges from 1000µA
• Always active with fast response time
• Features a zero-power voltage divider at selected voltages
• Equipped with matched current mirrors and current sources
• Includes a zero-power mode maximum voltage limiter

Available to order at Digi-Key and Mouser (product number ALD810027SCL) in 16-pin SOIC packages starting at $4.24 each per 100.